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    SubjectRe: usbfs, claiming entire usb devices
    On Fri, May 8, 2009 at 16:06, Alan Stern <> wrote:
    > On Fri, 8 May 2009, Kay Sievers wrote:
    >> You mentioned earlier, that you would need to match the holder of the
    >> "lock" and the one that accesses the device?
    > Yes.  That is, a process shouldn't be allowed to access a locked device
    > unless that process is the lock holder.

    You think the pid or the uid would make more sense?

    >> Wouldn't it be sufficient already, if you can take a "lock" at the
    >> specific port, that prevents the kernel to access the device when it
    >> shows up?
    > I don't know how the people requesting this feature would feel about
    > that.  They seem to want to lock out other processes as well as locking
    > out the kernel.

    Might be useful, yeah. I could think of use cases where a specific uid
    wants to lock a device, by holding the lock file open, and only the
    same uid (could be a different pid) can claim the device from

    >> You thought of supporting a number of different users, with different
    >> uids, or would that be a root-only action?
    > A typical use case would be somebody running an emulator like QEMU.  In
    > theory there could be multiple QEMU processes running concurrently,
    > each owning a different set of ports.  The uids might be different or
    > they might all be the same.
    > Setting the lock permissions would be up to userspace.

    Yeah, sounds fine.

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